HEVC Convert Bitrate

[severalboxes 0]

Been using handbrake for years to convert video files to hevc before adding media to Emby. Using a nvidia gpu for hardware acceleration.

I recently discovered that Emby has the convert feature built right in. However I haven't been able to get the output file to have a video bitrate of anything other than 2 mbps. This is also using nvidia gpu for hardware acceleration. When choosing convert, I've tried all the options for quality, including custom, but it always ends up at 2 mbps. I downloaded the diagnostic options plugin, and I see additional settings in transcode for H264, but not HEVC. Here's a snippet from the log file showing the 2000 kb/s. Am I overlooking something obvious here?

Thanks

 

15:14:54.539 encoder : Lavf59.17.100

15:14:54.539 Stream #0:0: Video: hevc (Main), cuda(tv, bt709, progressive), 1920x1080 [SAR 1:1 DAR 16:9], q=2-31, 2000 kb/s, 23.98 fps, 1k tbn

 

 

[Abobader 3469]

Hello severalboxes,

** This is an auto reply **

Please wait for someone from staff support or our members to reply to you.

It's recommended to provide more info, as it explain in this thread:

Thank you.

Emby Team

[Luke 42083]

Hi, can you please provide an example and attach the complete log files? Thanks.

[severalboxes 0]

On this try I believe I put 10 mbps as the custom bitrate, just messing around with it. Selecting 1.5 mbps will actually give about 1.5 mbps, but it really seems to top out at 2.5 mbps no matter what you choose.

 

 

ffmpeg-transcode-778a6bd4-be8b-4b44-bace-d62f26916e20_1.txt embyserver.txt

[Luke 42083]

Strange. We are passing the higher value into the encoder. As a test, if you disable hardware transcoding in server transcoding settings and then try again, how does that compare?

[rbjtech 5284]

The encoder will only use what it needs - just because you put 10Mbit, it is not going to use that unless it has to.   A 1080p encode with hevc is going to use around the 2-3 Mbit/sec mark as it's based on Constant Quality, not a Constant Bitrate Encode.

-maxrate:v:0 8798816 

This is the max value passed into ffmpeg (from your log) - the other bit's (1.2Mbit) are reserved for Audio.

If you want more control, then compare it against something like Handbrake - with the same CQ value of 22/23 - and it will likely be about the same bitrate.

The key thing here is QUALITY - does the output look comparable to the original VC1 encode ?  if yes, then it doesn't matter that it's only ~2Mbit - as that is all the encoder needed.

 

Edited August 28, 2023 by rbjtech

[severalboxes 0]

I've messed around with using the software encoder with similar results, the higher bitrate and visual quality just isn't there. To be fair Handbrake using a software decoder makes it not really an apples to apples comparison. I'm just gonna continue using handbrake for original conversions. Luke I appreciate you looking into it.

 

Thanks